The invention relates to a method of making a shaft seal ring wherein a ring-forming element is flared into the seal ring.
A method of this type is known from published German patent application DOS No. 24 60 185. There, the ring-forming element is cut from a thick-walled tube of polytetrafluoroethylene (PTFE), provided on one of its two axial boundary surfaces in the vicinity of the inner periphery with a hydrodynamically-acting return zone by cutting or stamping, and then turned out in this area so that a conical projection is produced. The wall thickness of the projection is thus reduced. As this is the area exposed to the abrasive action of the machine shaft which moves relative to it, this reduces the wear volume, and also results in poor flexibility for response to radial shaft oscillations. The turning operation also gives the molecular structure of the material at the dynamic return zone an orientation in the longitudinal direction which makes it difficult to achieve uniform contact pressures over long periods of time. Moreover, the production process does not lend itself to being atomated since production, shaping and mounting the sealing element in the reinforcing ring are difficult to accomplish, especially in a compact unit.